A layered double hydroxide composite electrode material for aqueous ammonium-ion batteries and a preparation method thereof

Abstract

This invention belongs to the field of ammonium-ion battery technology, specifically relating to a layered double hydroxide (LDHs) composite electrode material for aqueous ammonium-ion batteries and its preparation method. This invention provides a method for preparing layered double hydroxide composite electrode materials using an ultrafast cyclic voltammetric electrodeposition (CVD) method. This method, by introducing an ultrafast CVD method, achieves enhanced control over the deposition kinetics process, thereby obtaining a defect-enriched LDHs composite electrode material with excellent structural characteristics and ammonium storage performance. The method does not require high temperature and high pressure conditions, and can rapidly achieve one-step in-situ construction of high-performance LDHs composite electrode materials at room temperature, offering advantages such as simple preparation process, short time, and low energy consumption. Moreover, this ultrafast CVD deposition strategy exhibits similar structural control effects in different LDH systems, indicating its good versatility in the preparation of layered double hydroxide electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of ammonium-ion battery technology, specifically relating to a layered double hydroxide composite electrode material for aqueous ammonium-ion batteries and its preparation method. Background Technology

[0002] With population growth and continuous urbanization, traditional fossil fuels are gradually being depleted, and environmental problems such as the greenhouse effect are becoming increasingly prominent, making innovation and development of energy technologies particularly important. While renewable energy sources such as nuclear, wind, tidal, and solar power have broad application prospects, their intermittent and uncontrollable nature limits their practical application. Therefore, developing electrochemical energy storage devices with high energy density, high efficiency, and flexible application has become a key research focus.

[0003] Lithium-ion batteries (LIBs) dominate the energy storage field due to their high energy density and superior cycle stability, but they still face many bottlenecks: organic electrolytes are prone to decomposition or side reactions, leading to thermal runaway, combustion, or even explosions, posing serious safety hazards; stringent assembly conditions result in high manufacturing costs; and lithium metal reserves are limited, making it difficult to meet the needs of long-term sustainable development. Therefore, developing new alternative energy storage systems is of significant strategic importance.

[0004] Aqueous ammonium-ion batteries (AIBs), as an emerging energy storage system, have advantages such as low manufacturing cost, non-toxic electrolyte, non-volatile and non-flammable electrolyte, and abundant raw materials. Firstly, their electrolytes are typically neutral or weakly acidic aqueous solutions, which are not only non-toxic and non-flammable but also effectively prevent severe electrode corrosion and improve battery cycle stability. Secondly, ammonium ions (NH4+) act as charge carriers... + Ammonium ion (NH4) has a smaller hydrated ionic radius (approximately 0.331 nm), making it easier to insert into / extract from electrode materials compared to lithium ions (approximately 0.382 nm) and sodium ions (approximately 0.358 nm), thus endowing ammonium ion batteries with excellent ion diffusion kinetics. Furthermore, NH4... + The unique tetrahedral structure and hydrogen bonding ability provide more flexibility and potential for the design of electrode materials.

[0005] However, while aqueous ammonium-ion batteries possess the aforementioned advantages, their low electrode material energy density, narrow potential window, and limited cycle life make them unsuitable for meeting the practical needs of future high-performance electrochemical energy storage devices. Therefore, developing high-performance aqueous ammonium-ion battery electrode materials remains a key research direction in this field. Among numerous cathode materials, layered double hydroxides (LDHs) are abundant, simple to synthesize, exhibit excellent performance, and are environmentally friendly and pollution-free. As a class of ionic layered compound electrode materials, they show broad application prospects in ammonium-ion energy storage devices. The general formula for LDHs is [M... 2+1-x M 3+ x (OH)2] x+ [A n - ] x / n ·mH2O can optimize its physicochemical properties and electrochemical performance by adjusting the types and proportions of the constituent metal ions; its two-dimensional layered structure can provide abundant intercalation sites for charge carriers, and at the same time, it can bond with the materials within the layers, significantly improving the ion intercalation stability of the electrode material in aqueous batteries.

[0006] However, current LDH electrode materials still have significant technical defects in practical applications: First, their intrinsic conductivity is poor, and the two-dimensional layered structures synthesized by traditional methods are prone to curling and severe stacking, which can block ion transport channels and affect their rate performance and cycle stability in aqueous electrolytes. Second, traditional preparation processes such as hydrothermal methods, coprecipitation methods, and conventional electrochemical deposition methods are difficult to precisely control during nucleation and growth, often resulting in low nucleation density, long crystal growth time, and the formation of layered systems with high crystallinity and limited electrochemical reactive sites, which is not conducive to building efficient electrode / electrolyte interfaces and fast ion transport channels.

[0007] Currently, the main methods for preparing electrode materials for LDHs ammonium ion batteries include hydrothermal methods, coprecipitation methods, and electrochemical deposition methods. However, these methods still have many shortcomings: (1) Hydrothermal / coprecipitation methods and other liquid-phase chemical methods are complex and the structure is uncontrollable: These methods usually require a long reaction time (several hours to tens of hours) and complex post-processing steps, resulting in a long preparation cycle and high energy consumption. Moreover, the preparation process depends on solution chemical reactions, and the deposition position and thickness of the material on the substrate are difficult to control precisely. They often require subsequent coating or adhesive to assist in film formation, which increases the interfacial resistance and the proportion of inactive components. (2) Conventional electrochemical deposition methods have limited structural control capabilities: In conventional methods such as constant potential, constant current, and pulse, the electrode is usually in a single or segmented polarization state. The deposition process lacks a dynamic control mechanism and cannot achieve continuous material transfer and interfacial reaction under electric field drive. It is easy to have local over-deposition, structural inhomogeneity, or the formation of thick layers and agglomerates, which reduces the utilization rate of active sites. At the same time, these methods are difficult to precisely control the nucleation rate and growth behavior, which is not conducive to building an efficient electrode / electrolyte interface. (3) Conventional low scan rate CV electrodeposition has problems of insufficient nucleation density and uncontrolled growth: Existing cyclic voltammetric deposition mostly uses a low scan rate of tens to hundreds of millivolts per second. Although it is beneficial for electric field-driven mass transfer, the electrode potential changes slowly and the deposition process is close to a quasi-steady state. The material may be more inclined to undergo slow epitaxial growth and lamellar stacking, forming a structure with high crystallinity. The generation of defect sites is limited, which in turn limits electrochemical activity.

[0008] Therefore, it is still necessary to develop a simple, fast, structurally controllable, and universally applicable preparation method for LDH electrode materials to effectively control the nucleation and growth process of the materials and obtain materials more favorable for NH4+. + The layered structure of the storage further enhances its overall electrochemical performance in aqueous ammonium-ion batteries. Summary of the Invention

[0009] To address the common problems in the preparation of existing LDH electrode materials, such as complex processes, low utilization of active sites, and limited ion transport, this invention proposes a method for preparing layered double hydroxide (LDH) composite electrode materials based on ultrafast cyclic voltammetry (UFCV) electrochemical deposition. This method is applicable to various LDH systems (such as Co-Ni-LDHs, Ni-Mn-LDHs, Mn-Al-LDHs, Mn-Co-LDHs, Ni-Fe-LDHs, Zn-Al-LDHs, Co-Fe-LDHs, Ni-Mn-Co-LDHs, etc.) and exhibits good structural controllability and versatility.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a method for preparing a layered double hydroxide composite electrode material suitable for ammonium ion batteries, comprising the following steps: placing a conductive current collector in a precursor solution containing metal cations, and using an ultrafast cyclic voltammetric electrodeposition method to grow layered double hydroxides (LDHs) in situ on the surface of the conductive current collector by potential scanning within a set potential window; The ultrafast cyclic voltammetric electrodeposition method, compared to the low scan rate process typically used in conventional electrochemical deposition of layered double hydroxides, specifically refers to a scan rate exceeding 1000 mV / s. This method is used to control the deposition kinetics at the electrode interface, achieving high-density nucleation through continuous polarization-depolarization during deposition and suppressing excessive crystal growth. This results in layered double hydroxides (LDHs) exhibiting low crystallinity and defect enrichment, ultimately yielding composite electrode materials with numerous electrochemical active sites and excellent electrochemical performance (i.e., layered double hydroxide composite electrode materials suitable for ammonium-ion batteries).

[0011] Preferably, the preparation method of the layered double hydroxide composite electrode material includes the following steps: using a two-electrode system or a three-electrode system, with a conductive current collector as the working electrode and a precursor solution containing metal cations as the electrolyte, cyclic voltammetry is performed at an ultrafast scan rate of over 1000 mV / s within a set potential window to achieve in-situ deposition of layered double hydroxides (LDHs) on the surface of the conductive current collector; the layered double hydroxides (LDHs) are selected from one or more combinations of bimetallic or multimetallic layered double hydroxide (LDHs) systems such as Co-Ni, Ni-Mn, Mn-Al, Mn-Co, Ni-Fe, Co-Fe, Zn-Al, and Ni-Mn-Co, and the precursor solution contains metal cations corresponding to the selected layered double hydroxides (LDHs).

[0012] More preferably, the ultrafast scan rate is 1000 to 10000 mV / s.

[0013] The ultrafast cyclic voltammetric electrodeposition method described in this invention refers to an electrochemical deposition method in which a continuously linearly varying potential is applied to the working electrode within a preset potential window at a scan rate significantly higher than that of conventional cyclic voltammetric deposition. This allows for rapid and repetitive polarization-depolarization processes on the electrode surface within a short time, inducing high-density nucleation and controlled growth of active components on the substrate surface. The "ultrafast" aspect of this invention preferably refers to a scan rate of 1000 mV / s or higher, more preferably 5000–10000 mV / s.

[0014] Compared with existing technologies, on the one hand, the ultrafast CV deposition method significantly improves the instantaneous nucleation density while ensuring electric field-driven mass transfer, effectively suppressing continuous crystal growth and making the resulting LDHs structure exhibit low crystallinity or even amorphous characteristics, which is conducive to increasing the number of defect sites and active centers; on the other hand, the large number of defects in the electrodes prepared by this method is also conducive to optimizing ion transport paths and enhancing ion transport kinetics.

[0015] Compared to pulsed electrodeposition, this continuous variation process is beneficial for continuously driving the migration and diffusion of ions in the solution during deposition, thereby improving the material transport efficiency under the action of the electric field. At the same time, the interfacial reaction is continuously controlled through a gradual polarization process, making the deposition process more uniform and stable.

[0016] Furthermore, this method does not require high temperature and high pressure conditions, and can rapidly achieve one-step in-situ construction of high-performance LDHs composite electrode materials at room temperature, offering advantages such as simple preparation process, short preparation time, and low energy consumption. Moreover, this ultrafast cyclic voltammetric deposition strategy exhibits a consistent trend of improved electrochemical performance in different LDHs systems, indicating its potential for further application in the preparation of layered double hydroxide electrode materials.

[0017] More preferably, the metal cation is derived from one or more combinations of its nitrate, chloride, sulfate, acetate, and other metal-soluble salts.

[0018] More preferably, the set potential window is -1.5 to 0.2 V relative to the saturated calomel electrode (vs. SCE), and even more preferably -1.3 to 0.1 V (vs. SCE).

[0019] More preferably, the conductive current collector is one or more of carbon nanotubes, carbon cloth, graphene, carbon fiber, metal substrate, and conductive glass.

[0020] More preferably, the layered double hydroxides (LDHs) are Co-Ni or Ni-Mn bimetallic layered double hydroxides (Co-Ni-LDHs or Ni-Mn-LDHs).

[0021] More preferably, the cyclic voltammetric scan employs a three-electrode system, wherein the counter electrode is an inert electrode, and the reference electrode includes a saturated calomel electrode or an Ag / AgCl electrode.

[0022] The second aspect of the present invention also provides a layered double hydroxide composite electrode material prepared by the preparation method described in the first aspect.

[0023] The third aspect of the present invention also provides the application of the layered double hydroxide composite electrode material described in the second aspect in an aqueous ammonium ion battery.

[0024] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention effectively regulates the nucleation and growth process of LDHs through ultrafast cyclic voltammetric electrodeposition, so that the material presents a low crystallinity and defect-rich structure, thereby providing more electrochemical reaction active sites and significantly improving the ammonium storage performance of the electrode material.

[0025] (2) The LDHs electrode material prepared by the method of the present invention has better ion transport conditions and can effectively shorten the NH4+ ion transport time. + The transport path within the material is favorable for NH4. + Rapid insertion / extraction reduces impedance, thereby effectively improving rate performance and the reversibility of electrochemical reactions.

[0026] (3) The method of the present invention is simple and efficient, and can realize the one-step in-situ construction of electrode materials under normal temperature conditions.

[0027] (4) The method of the present invention exhibits similar structural regulation and performance improvement effects in different LDHs systems, and has good versatility and industrial application potential. Attached Figure Description

[0028] Figure 1 The images show a comparison of SEM images of the composite electrodes in Example 1 and Comparative Example 1.

[0029] Figure 2 The XRD patterns of the composite electrodes in Example 1 and Comparative Example 1 are shown in comparison.

[0030] Figure 3 The GCD curves (current density 1 A / g) of the composite electrodes in Example 1 and Comparative Example 1 in ammonium acetate electrolyte are shown.

[0031] Figure 4 This is a comparison chart of the specific capacity of the composite electrodes in Example 1 and Comparative Example 1 at different rates in ammonium acetate electrolyte.

[0032] Figure 5 The image shows a comparison of the electrochemical impedance spectroscopy of the composite electrodes in Example 2 and Comparative Example 2 in ammonium sulfate electrolyte.

[0033] Figure 6 The graph shows the specific capacity of the composite electrodes in Example 3 and Comparative Example 3 in ammonium acetate electrolyte (current density is 1 A / g).

[0034] Figure 7 The image shows a comparison of the cyclic voltammetry curves of the composite electrodes in Example 1 and Comparative Example 4 in ammonium acetate electrolyte (scan rate 5 mV / s). Detailed Implementation

[0035] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0037] This invention provides an electrode material preparation method that can effectively control the nucleation and growth process of layered double hydroxides, while also being simple in process, highly efficient in preparation, and with strong structural control capabilities. This method introduces an ultrafast cyclic voltammetric electrodeposition method to achieve enhanced control of the deposition kinetics process, thereby obtaining a defect-enriched LDHs composite electrode material with excellent structural characteristics and ammonium storage performance. Moreover, this method is applicable to different LDHs systems and has good universality.

[0038] The core technology of this invention lies in: utilizing the rapidly changing potential scan during ultrafast cyclic voltammetric electrodeposition to achieve dynamic control of nucleation and growth behavior at the electrode interface. By increasing the scan rate, a rapidly changing unsteady deposition environment is constructed at the electrode interface, causing the electrode surface to undergo a high-frequency polarization-depolarization process in a short time. This significantly increases the instantaneous nucleation rate and inhibits excessive crystal growth, while simultaneously achieving coherent mass transfer and interfacial reactions driven by the electric field. The resulting LDHs exhibit low crystallinity and defect-rich structural characteristics. This type of structure provides more low-coordination sites and electrochemically active sites, thereby improving the specific capacity of the electrode material. Furthermore, this structure facilitates the construction of continuous ion transport channels and improves the electrode / electrolyte interfacial reaction conditions, enabling NH4+ to... + The transport path in the material is shortened, the resistance to ion diffusion is reduced, thereby improving the ion transport kinetics performance of the electrode material.

[0039] The basic method of this invention is as follows: electrochemical deposition is performed using a two-electrode or three-electrode system (a three-electrode system is preferred for precise control of the deposition potential). The working electrode is a conductive current collector (e.g., carbon nanotube film, carbon cloth, or other conductive materials), the counter electrode is an inert electrode (e.g., a platinum sheet), and the reference electrode is a saturated calomel electrode, Ag / AgCl electrode, or similar electrode. A precursor solution containing the target metal cation is used as the electrolyte, and cyclic voltammetry is performed under a set potential window and ultrafast scan rate to achieve in-situ deposition of LDHs on the substrate surface. By adjusting the scan rate, potential window, and number of cycles, the kinetics of the deposition process can be controlled to optimize the material's structural morphology and interface state. After deposition, the resulting electrode material can be electrochemically activated (e.g., pretreated with low-scan-rate cyclic voltammetry in an alkaline electrolyte) to further adjust the surface chemical state and increase the exposure of active sites.

[0040] The key advantages of this invention are: by enhancing and controlling the electrodeposition kinetics, the structure, interface, and performance of LDHs electrode materials are synergistically optimized. Compared with traditional preparation methods, this invention offers advantages such as simple process, short preparation time, no need for high-temperature and high-pressure conditions, and the ability to construct higher-performance LDHs electrodes in situ in one step, which helps reduce energy consumption and production costs. Moreover, this invention's method exhibits consistent structural control effects in different LDHs systems, demonstrating good versatility and application prospects.

[0041] To fully and clearly present the technical solution and significant advantages of the present invention, the present invention will be described in detail below with reference to specific embodiments.

[0042] Example 1: An aqueous ammonium-ion battery composite electrode (CNT@Co-Ni-LDHs composite electrode) and its preparation method. (1) The carbon nanotube film cut into 1 cm × 1 cm size was soaked in concentrated sulfuric acid with a mass fraction of about 98% for 5 h, washed with deionized water and anhydrous ethanol in turn, and then dried.

[0043] (2) Dissolve 0.48 g Co(NO3)2·6H2O and 0.24 g Ni(NO3)2·6H2O in 50 mL of deionized water, and stir thoroughly at room temperature to obtain Co. 2+ Ni 2+ A precursor mixture with a content ratio of 2:1 and a total cation concentration of 0.05 M.

[0044] (3) A standard three-electrode system was adopted, with a saturated calomel electrode (SCE) as the reference electrode, a platinum sheet as the counter electrode, the carbon nanotube film pretreated in step (1) as the working electrode, and the precursor mixture prepared in step (2) as the electrolyte. Cyclic voltammetry electrodeposition was performed under a voltage window of -1.2 to -0.6 V and a scan rate of 5000 mV / s, and CNT@Co-Ni-LDHs composite electrode was obtained after 1800 cycles.

[0045] (4) The CNT@Co-Ni-LDHs composite electrodes obtained in steps (1) to (3) are washed and dried before being subjected to SEM and XRD tests.

[0046] (5) The CNT@Co-Ni-LDHs composite electrode obtained in steps (1) to (3) was subjected to electrochemical activation treatment, specifically as follows: a standard three-electrode system was adopted, with SCE as the reference electrode, the CNT@Co-Ni-LDHs composite electrode as the working electrode, and a platinum sheet as the counter electrode. The CNT@Co-Ni-LDHs composite electrode was electrochemically activated by cyclic voltammetry in 0.5 M KOH solution at 0–0.5 V, 10 mV / s, and 3 cycles. Subsequently, its electrochemical performance was tested, including cyclic voltammetry and constant current charge-discharge tests, and the discharge specific capacity at different current densities was calculated from the charge-discharge curves. The electrolyte used in the electrochemical tests was 1 M NH4Ac solution.

[0047] Example 2: An aqueous ammonium-ion battery composite electrode (CC@Co-Ni-LDHs composite electrode) and its preparation method. (1) The cut carbon cloth of 1 cm × 1 cm size is washed with deionized water and anhydrous ethanol and then dried.

[0048] (2) Dissolve 0.64 g Co(NO3)2·6H2O and 0.37 g Ni(NO3)2·6H2O in 50 mL of deionized water, and stir thoroughly at room temperature to obtain Co. 2+Ni 2+ A precursor mixture with a content ratio of 2:1 and a total cation concentration of 0.05 M.

[0049] (3) A standard three-electrode system was adopted, with SCE as the reference electrode, platinum sheet as the counter electrode, carbon cloth from step (1) as the working electrode, and precursor mixture prepared in step (2) as the electrolyte. Cyclic voltammetry electrodeposition was performed under a voltage window of -1.1 to -0.5 V and a scan rate of 10000 mV / s for 2000 cycles to obtain CC@Co-Ni-LDHs composite electrode.

[0050] (4) The CC@Co-Ni-LDHs composite electrode obtained in steps (1) to (3) was subjected to electrochemical activation treatment. Specifically, a standard three-electrode system was used, with SCE as the reference electrode, CC@Co-Ni-LDHs composite electrode as the working electrode, and platinum sheet as the counter electrode. The CC@Co-Ni-LDHs composite electrode was electrochemically activated by cyclic voltammetry in 0.5 M KOH solution at 0–0.6 V, 25 mV / s, and 2 cycles, and electrochemical impedance spectroscopy was performed. The electrolyte used in the test was 1 M (NH4)2SO4 solution.

[0051] Example 3: An aqueous ammonium-ion battery composite electrode (CNT@Ni-Mn-LDHs composite electrode) and its preparation method. (1) The carbon nanotube film cut into 1 cm × 1 cm size was soaked in concentrated sulfuric acid with a mass fraction of about 98% for 5 h, washed with deionized water and anhydrous ethanol in turn, and then dried.

[0052] (2) Dissolve 0.240 g Ni(NO3)2·6H2O, 0.270 g MnSO4·H2O, 0.036 g CO(NH2)2, and 0.0185 g NH4F in 50 mL of deionized water, and add 0.085 mL of 30% hydrogen peroxide aqueous solution. After stirring thoroughly at room temperature, a precursor mixture with a Mn to Ni element content ratio of 2:1 is obtained.

[0053] (3) A standard three-electrode system was adopted, with SCE as the reference electrode, platinum sheet as the counter electrode, carbon nanotube film pretreated in step (1) as the working electrode, and precursor mixture prepared in step (2) as the electrolyte. Cyclic voltammetry electrodeposition was performed in a voltage window of -1.3 to 0.1 V and a scan rate of 5000 mV / s for 3000 cycles to obtain CNT@Ni-Mn-LDHs composite electrode.

[0054] (4) The CNT@Ni-Mn-LDHs composite electrode obtained in steps (1) to (3) was subjected to electrochemical activation treatment. Specifically, a standard three-electrode system was used, with SCE as the reference electrode, the CNT@Ni-Mn-LDHs composite electrode as the working electrode, and a platinum sheet as the counter electrode. The CNT@Ni-Mn-LDHs composite electrode was electrochemically activated by cyclic voltammetry in 1 M KOH solution at 0–0.6 V, 100 mV / s, and 5 cycles. The activated CNT@Ni-Mn-LDHs composite electrode was used for constant current charge-discharge testing, and the discharge specific capacity was calculated from the charge-discharge curve. The electrolyte used in the test was 1 M NH4Ac solution.

[0055] Comparative Example 1: An aqueous ammonium-ion battery composite electrode (CNT@Co-Ni-LDHs composite electrode) and its preparation method (1) The carbon nanotube film cut into 1 cm × 1 cm size was soaked in concentrated sulfuric acid with a mass fraction of about 98% for 5 h, washed with deionized water and anhydrous ethanol in turn, and then dried.

[0056] (2) Dissolve 0.48 g Co(NO3)2·6H2O and 0.24 g Ni(NO3)2·6H2O in 50 mL of deionized water, and stir thoroughly at room temperature to obtain Co. 2+ Ni 2+ A precursor mixture with a content ratio of 2:1 and a total cation concentration of 0.05 M.

[0057] (3) A standard three-electrode system was adopted, with SCE as the reference electrode, platinum sheet as the counter electrode, carbon nanotube film pretreated in step (1) as the working electrode, and precursor mixture prepared in step (2) as the electrolyte. Cyclic voltammetry electrodeposition was performed in a voltage window of -1.2 to -0.6 V and a scan rate of 100 mV / s to obtain CNT@Co-Ni-LDHs composite electrode.

[0058] (4) The CNT@Co-Ni-LDHs composite electrodes obtained in steps (1) to (3) are washed and dried before being subjected to SEM and XRD tests.

[0059] (5) The CNT@Co-Ni-LDHs composite electrode obtained in steps (1) to (3) was subjected to electrochemical activation treatment. Specifically, a standard three-electrode system was used, with SCE as the reference electrode, the CNT@Co-Ni-LDHs composite electrode as the working electrode, and a platinum sheet as the counter electrode. The CNT@Co-Ni-LDHs composite electrode was electrochemically activated by cyclic voltammetry in 0.5 M KOH solution at 0–0.5 V, 10 mV / s, and 3 cycles. After activation, it was used for constant current charge-discharge testing, and the discharge specific capacity at different current densities was calculated from the charge-discharge curves. The electrolyte used in the test was 1 M NH4Ac solution.

[0060] Comparative Example 2: An aqueous ammonium-ion battery composite electrode (CC@Co-Ni-LDHs composite electrode) and its preparation method (1) The cut carbon cloth of 1 cm × 1 cm size is washed with deionized water and anhydrous ethanol and then dried.

[0061] (2) Dissolve 0.64 g Co(NO3)2·6H2O and 0.37 g Ni(NO3)2·6H2O in 50 mL of deionized water, and stir thoroughly at room temperature to obtain Co. 2+ Ni 2+ A precursor mixture with a content ratio of 2:1 and a total cation concentration of 0.05 M.

[0062] (3) A standard three-electrode system was adopted, with SCE as the reference electrode, platinum sheet as the counter electrode, carbon cloth from step (1) as the working electrode, and precursor mixture prepared in step (2) as the electrolyte. Cyclic voltammetry electrodeposition was performed in a voltage window of -1.1 to -0.5 V and a scan rate of 100 mV / s to obtain CC@Co-Ni-LDHs composite electrode.

[0063] (4) The CC@Co-Ni-LDHs composite electrode obtained in steps (1) to (3) was subjected to electrochemical activation treatment. Specifically, a standard three-electrode system was used, with SCE as the reference electrode, CC@Co-Ni-LDHs composite electrode as the working electrode, and platinum sheet as the counter electrode. The CC@Co-Ni-LDHs composite electrode was subjected to cyclic voltammetry electrochemical activation in 0.5 M KOH solution at 0–0.6 V, 25 mV / s, and 2 cycles for electrochemical impedance spectroscopy testing. The electrolyte used for the test was 1 M (NH4)2SO4 solution.

[0064] Comparative Example 3: An aqueous ammonium-ion battery composite electrode (CNT@Ni-Mn-LDHs composite electrode) and its preparation method (1) The carbon nanotube film cut into 1 cm × 1 cm size was soaked in concentrated sulfuric acid with a mass fraction of about 98% for 5 h, washed with deionized water and anhydrous ethanol in turn, and then dried.

[0065] (2) Dissolve 0.240 g Ni(NO3)2·6H2O, 0.270 g MnSO4·H2O, 0.036 g CO(NH2)2, and 0.0185 g NH4F in 50 mL of deionized water, and add 0.085 mL of 30% hydrogen peroxide aqueous solution. After stirring thoroughly at room temperature, a precursor mixture with a Mn to Ni element content ratio of 2:1 is obtained.

[0066] (3) A standard three-electrode system was adopted, with SCE as the reference electrode, platinum sheet as the counter electrode, carbon nanotube film pretreated in step (1) as the working electrode, and precursor mixture prepared in step (2) as the electrolyte. Cyclic voltammetry electrodeposition was performed in a voltage window of -1.3 to 0.1 V and a scan rate of 5 mV / s to obtain CNT@Ni-Mn-LDHs composite electrode.

[0067] (4) The CNT@Ni-Mn-LDHs composite electrode obtained in steps (1) to (3) was subjected to electrochemical activation treatment. Specifically, a standard three-electrode system was used, with SCE as the reference electrode, the CNT@Ni-Mn-LDHs composite electrode as the working electrode, and a platinum sheet as the counter electrode. The CNT@Ni-Mn-LDHs composite electrode was electrochemically activated by cyclic voltammetry in 1 M KOH solution at 0–0.6 V, 100 mV / s, and 5 cycles. The activated CNT@Ni-Mn-LDHs composite electrode was used for constant current charge-discharge testing, and the discharge specific capacity was calculated from the charge-discharge curve. The electrolyte used in the test was 1 M NH4Ac solution.

[0068] Comparative Example 4: An aqueous ammonium-ion battery composite electrode (CNT@Co-Ni-LDHs composite electrode) and its preparation method (1) The carbon nanotube film cut into 1 cm × 1 cm size was soaked in concentrated sulfuric acid with a mass fraction of about 98% for 5 h, washed with deionized water and anhydrous ethanol in turn, and then dried.

[0069] (2) Dissolve 0.48 g Co(NO3)2·6H2O and 0.24 g Ni(NO3)2·6H2O in 50 mL of deionized water, and stir thoroughly at room temperature to obtain Co. 2+ Ni 2+ A precursor mixture with a content ratio of 2:1 and a total cation concentration of 0.05 M.

[0070] (3) A standard three-electrode system was adopted, with SCE as the reference electrode, platinum sheet as the counter electrode, carbon nanotube film pretreated in step (1) as the working electrode, and precursor mixture prepared in step (2) as the electrolyte. Step potential deposition was performed between -1.2 V and -0.6 V under magnetic stirring (320 r / min), with a pulse width of 0.12 s and a duty cycle of 50% (the high and low potential times in a single cycle were both 0.06 s), to obtain the CNT@Co-Ni-LDHs composite electrode prepared by step potential deposition.

[0071] (4) The CNT@Co-Ni-LDHs composite electrode obtained in steps (1) to (3) was subjected to electrochemical activation treatment. Specifically, a standard three-electrode system was used, with SCE as the reference electrode, the CNT@Co-Ni-LDHs composite electrode as the working electrode, and a platinum sheet as the counter electrode. The CNT@Co-Ni-LDHs composite electrode was electrochemically activated by cyclic voltammetry in 0.5 M KOH solution at 0–0.5 V, 10 mV / s, and 3 cycles. The activated CNT@Co-Ni-LDHs composite electrode was then used for cyclic voltammetry testing. The electrolyte used in the test was 1 M NH4Ac solution.

[0072] The following are the characterization and performance test results and analysis of Examples 1-3 and Comparative Examples 1-4: like Figure 1 As shown, the CNT@Co-Ni-LDHs electrode in Example 1 exhibits a uniformly distributed, wrinkled nanosheet structure. The nanosheets are interwoven and relatively loose, which is conducive to the formation of a more disordered open microstructure network. In contrast, the CNT@Co-Ni-LDHs nanosheet structure in Comparative Example 1 is more regular and ordered, with the nanosheets more tightly bound. This indicates that ultrafast cyclic voltammetric deposition can effectively regulate the nucleation and growth process of Co-Ni-LDHs, inhibit excessive growth and accumulation of sheets, and make the material more disordered, forming richer structural defects and active sites.

[0073] like Figure 2 As shown, the CNT@Co-Ni-LDHs electrode in Example 1 exhibits significantly broadened and reduced intensity diffraction peaks on its (003) and (006) crystal planes, indicating lower crystallinity, higher amorphization, and more disordered structures and defects in the material. This suggests that ultrafast CV deposition is beneficial for constructing a low-crystallinity, defect-rich LDHs active layer, thereby providing more reaction sites.

[0074] like Figure 3 As shown, the CNT@Co-Ni-LDHs electrode in Example 1 exhibited a high 273 mAh·g under the same test conditions. -1The higher discharge specific capacity and smoother voltage plateau during discharge indicate stronger ammonium storage capacity and faster reaction kinetics. This demonstrates that ultrafast CV deposition can effectively optimize the microstructure of Co-Ni-LDHs on conductive substrates and improve their ammonium storage performance.

[0075] like Figure 4 As shown, the CNT@Co-Ni-LDHs electrode in Example 1 consistently exhibits higher discharge specific capacity and better rate performance at different current densities, even at 10 A·g -1 It can still maintain 205 mAh·g at high current density -1 The capacity demonstrates good capacity retention capability.

[0076] like Figure 5 As shown, the ohmic resistance R of the CC@Co-Ni-LDHs composite electrode in Example 2 is... s The conductivity is significantly lower than that of Comparative Example 2, indicating superior overall conductivity. The semi-circular diameter in the high-frequency region of Example 2 is smaller than that of Comparative Example 2, indicating that its charge transfer impedance R... ct The lower value indicates that ultrafast cyclic voltammetry deposition helps improve the charge transfer process at the electrode / electrolyte interface. Furthermore, the diffusion impedance parameter of Example 2 is slightly lower than that of Comparative Example 2, indicating that its ion transport process is also improved to some extent. This is mainly attributed to the low-crystallinity, defect-enriched Co-Ni-LDHs structure induced by ultrafast CV deposition. This structure can provide more disordered active sites and open transport channels, thereby improving ion transport kinetics and enhancing interfacial reaction kinetics.

[0077] like Figure 6 As shown, at 1 A·g -1 At the specified current density, the CNT@Ni-Mn-LDHs composite electrode in Example 3 exhibits a significantly higher discharge specific capacity than that in Comparative Example 3, demonstrating a capacity improvement of approximately four times. This indicates that the ultrafast CV deposition strategy can effectively optimize electrode structure and reaction kinetics in the Ni-Mn-LDHs system.

[0078] like Figure 7 As shown, the CNT@Co-Ni-LDHs electrode in Example 1 exhibits a larger enclosing area and a higher redox peak current in its cyclic voltammetry curve, with a more symmetrical shape. This indicates that the Co / Ni active sites in the Co-Ni-LDHs electrode material obtained by ultrafast CV deposition participate in the redox reaction to a greater extent, resulting in faster electrochemical reaction kinetics, higher electrochemical activity, and stronger ammonium storage capacity. This is because the potential continuously changes within a set window during ultrafast CV deposition, which is beneficial for continuously driving ion migration and ensuring mass transfer during deposition, thereby regulating the reaction process. This allows for improved electrochemical activity while maintaining a relatively stable and uniform deposition process.

[0079] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing a layered double hydroxide composite electrode material suitable for ammonium ion batteries, characterized in that, Includes the following steps: The conductive current collector is placed in a precursor solution containing metal cations, and the layered double hydroxide is grown in situ on the surface of the conductive current collector by potential scanning within a set potential window using an ultrafast cyclic voltammetric electrodeposition method. The ultrafast cyclic voltammetric electrodeposition method has a scan rate exceeding 1000 mV / s, which is used to control the deposition kinetics of the electrode interface. High-density nucleation is achieved through rapid and continuous polarization-depolarization during the deposition process, and excessive crystal growth is suppressed. This results in the layered double hydroxide exhibiting low crystallinity and defect enrichment characteristics, ultimately obtaining a layered double hydroxide composite electrode material suitable for ammonium-ion batteries.

2. The method for preparing a layered double hydroxide composite electrode material suitable for ammonium-ion batteries according to claim 1, characterized in that, The method includes the following steps: using a two-electrode or three-electrode system, with a conductive current collector as the working electrode and a precursor solution containing metal cations as the electrolyte, cyclic voltammetry is performed at an ultrafast scan rate exceeding 1000 mV / s within a set potential window to achieve in-situ deposition of layered double hydroxides on the surface of the conductive current collector; the layered double hydroxides include at least one of Co-Ni, Ni-Mn, Mn-Al, Mn-Co, Ni-Fe, Co-Fe, Zn-Al, Ni-Mn-Co bimetallic or multimetallic layered double hydroxides, and the precursor solution contains metal cations corresponding to the selected layered double hydroxides.

3. The method for preparing a layered double hydroxide composite electrode material suitable for ammonium-ion batteries according to claim 2, characterized in that, The ultrafast scan rate is 1000–10000 mV / s.

4. The method for preparing a layered double hydroxide composite electrode material suitable for ammonium-ion batteries according to claim 2, characterized in that, The metal cation is derived from one or more combinations of its nitrate, chloride, sulfate, and acetate.

5. The method for preparing a layered double hydroxide composite electrode material suitable for ammonium-ion batteries according to claim 2, characterized in that, The set potential window is -1.5 to 0.2 V relative to the saturated calomel electrode.

6. The method for preparing a layered double hydroxide composite electrode material suitable for ammonium-ion batteries according to claim 2, characterized in that, The conductive current collector is one or more of the following materials: carbon nanotubes, carbon cloth, graphene, carbon fiber, metal substrate, and conductive glass.

7. The method for preparing a layered double hydroxide composite electrode material suitable for ammonium-ion batteries according to claim 2, characterized in that, The layered double hydroxide is a Co-Ni or Ni-Mn bimetallic layered double hydroxide.

8. The method for preparing a layered double hydroxide composite electrode material suitable for ammonium-ion batteries according to claim 2, characterized in that, The cyclic voltammetric scan employs a three-electrode system, wherein the counter electrode is an inert electrode, and the reference electrode includes a saturated calomel electrode or an Ag / AgCl electrode.

9. The layered double hydroxide composite electrode material prepared by the preparation method according to any one of claims 1-8.

10. The application of the layered double hydroxide composite electrode material according to claim 9 in an aqueous ammonium ion battery.

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